I second the furled leader suggestion--- then you can just replace 'tippets' based on the size of fly you are heaving. A general rule is to take the size of fly and divide by 3 (give or take a size or two)-- size 12 fly-- use a 4Xtippet. Size 6 fly-- use a 2X tippet. Of course, in the last example: size 6 fly, 2X tippet-- you could reliably use the same 2X for sizes 4 and 8 flies as well. This 'formula' will turn the sizes of flies over nicely in the cast and give them a realistic appearance in/on the water.

I fish mainly warmwater (like you sound like you are going to) and I use a furled leader and either 4# or 6# mono 'tippets'-- usually 4#. It is good to know the tippet sizes, but don't worry about sticking strictly to them too much....